Mercury switch



QPSOE antar- COWZJYZ 2 Shets-Sheet 4 if g I I ll-I-l\lll'r \l'v III-IIIIIIIIIEIIIIIIIIIIIM :IIIIIIIIIW IIIIIIIEIIIIIIIIIII IIIIIIII IIIIIIIIIIIIEIIIIIIII IIIEIIIIEIIIIIIIIIIIII III is gg VIII/lag ESE-JEF E- C. H. LARSON MERCURY SWITCH r/l/l/I/ll/l/l//l/ I 2%,??? IIIIIIIIIIII IIIIIIIIIIJIIIIIIIIW 2, 2 IIIIIIIIIIIIIIIII Original Fil ed June 1, 193a Dec. 17, 1940.

Dec. 17 '1940.

c. H. LARSON MERCURY SWITCH Original Filed June 1, 1936 2. Sheets-Sheet 2 M Q Q mvrsmon BY Card 15. Larson ATTORNEYS Reissued Dec. 17, 1940 UNlTED STAT-ES MERCURY Carl B. Larson, Elkhart,

Adlake Company, a corporation of Illinois Original No. 2,209,984,

rial No..82,855, June 1,

dated August 6, 1940, Se-

1936. Application for reissue September 30, 1940, Serial No. 360,004

18 Claims. (CL 200-112) When a formed ceramic piece is appliedto' a vitreous part of a mercury switch or similar device, it has been the practice to use cement for making'the bond. However, almost all cemerits contain substances which are undesirable to have in an hermetically sealed envelope and therefore should be avoided if possible.

I have found that certain ceramic material can be fused to certain borosilicate glasses that have been used for the envelopes of mercury switches and similar devices, and that the bond between the glass and the ceramic material, when thus joined, is actually stronger than either of the two materials. In other words, if a piece of glass is fused to ceramic material in'the manner' taught by this invention, and an eifort is made to break the two apart, the break will not come at the junction of the two materials.

The principal object of the invention, therefore, is to show the application of this principle to mercury switches, particularly of the mercury displacement type, as disclosed in Larson Patent #1967247, and thereby provide switch structures which have greater capacity to stand up under '20 severe conditions of .use over a long period of time.

Further and other objects and advantages will appear from the following description taken in connection with the accompanying drawings, in

which- Fig. 1 is a sectional view of a fast-acting plunger type mercury switch with a mercury to mercury contact, the central electrode consisting of a ceramic cup which is fused to the glass sleeve surrounding the central electrode;

Fig. 2 is a sectional view of a switch which is provided with a ceramic collar fused to the glass thimble which forms a part of the displacer. and which also has a formed piece of ceramic material fused to the side wall of the switch envelope adjacent to the side electrode; 7

Fig. 3 is a sectional view of a time delay mercury switch in which the time delay element of ceramic material is fused to the glass thimble which constitutes a part of the dlsplacer and in which a ceramic sleeve is fused to the sleeve around the central electrode;

Fig. 4 is'a fragmentary, sectional view of a time delay switch in whichthe ceramic thimble constituting the time delay element is mounted on the central electrode by a small piece of glass tubing fused to the top of the electrode and to the thimble; and I Fig. 5 is a graph showing, with some degree of approximation, the expansion curves for cercient of expansion at room temperature not tain ceramic and glass materials which are referred to in the specification and'claims.

Several preferred embodiments of the invention are shown in the drawings and will hereafter be described, but it will be understood that I the selection of these preferred embodiments is merely for the purpose of complying with section 4888 of the Revised Statutes and should not be construed as limiting the appended claims unless required by the prior art.

In all forms of the invention where a part of the switch is described as being made of glass, it will be understood, unless the contrary is specifled, 'that the glass is a borosllicate or other hard glass having a low coefllcient of expansion, such, for example, as 133A of the Corning Glass Works, Corning, New York, which I am informed has a percentage composition substantially as follows: I

NazO 6 Also, it will be understood that when a switch part is described as being of ceramic material, porous material, or refractory material, a material such, for example, as Alundum (Grade RA84, RA36O or RA98), a product of the Norton Company, Worcester, Massachusetts, is meant. Alundum, I am informed, is substantially pure A1201. Glass of the type disclosed in Warnke Patent #1,996,845, issued April 9, 1935, will also fuse satisfactorily with Alundum.

It is a well known fact that for glass to seal with molybdenum, it must have a linear coeih- 40 greater than 5.4 x 10 Coming glass 733A has a coefilcient oi expansion of approximately 5.0x10 at room temperature, which is sufliciently close to that of molybdenum to form a good seal. "Alundum has substantially the same coemcient of expansion. Obviously, if Warnke glass is to be used with molybdenum, the percentages for the ingredients must be chosen within the disclosure of that patent so that the glass will have a linear coefllcient of expansions at room temperature close to that of molybdenum, in all events not greater than 5.4 x 10.-.

It is not definitely known why these particular glasses and ceramic materials will form a satisfactory seal, but it is believed that there are grade of glass with the ceramic and the glass being sealed to it. Secondly, and possibly of greatest importance," is the fact that Alujndum,

in addition to having substantially the same coeflicient of expansion as 733A glass at room temperature, also has an expansion curve that is remarkably close to and almost coincident with the expansion curve for the glass even up to' its annealing temperature. This similarity in the shape and steepness of the expansion curves, taken in conjunction with the intermediate glass that isformed between the ceramic and glass sleeve, probably accounts for the highly successful seal that can be formed by following the teachings of this invention. Warnkeglass has an expansion curve which,

- if not exactly coincident with the expansion curve for Alundum, is at least substantially parallel to and sufliciently close to effect a satisfactory fused seal between the materials over wide ranges of temperature changes. 7

The expansion curve for molybdenum is also sumciently close to and substantially parallel with the corresponding curves for the glass and ceramic materials specified above'that no dimculty is encountered in sealing the glass to molybdenum to form a stable bond.

These various relationships are clearly shown in Fig. 5, in which the curves shown are approximations of the expansion curves for the materials indicated. It will be seen that the expansion curves for Alundum and-733A glass are never apart by more than 375 millionths per centimeter, even up to the fusion point of the glass, which is approximately 600 centigra'de. The glass indicated by the curve R will also fuse satisfactorily with Alundum, even though at 425 centigrade the two curves are apart by approximately 750 millionths per centimeter. The fact that curve A crosses the Alundum curve is of no consequence because the upturn in the curve merely brings the curves closer together and they do not move apart more than a tolerable amount until fusion-temperature is reached; Curves S, T and U represent the expansion curves of other glasses which will not fuse satisfactorily with Alundum due to the fact that the expansion curves-of these glasses are not sufficiently close to or parallel with the Alundum curve to form a satisfactory seal. Although the glass represented by curve 8 might form a satisfactory seal with Alundum at room temperature due to the proximity of the expansion curves at that temperature, the rates of expansion differ too greatly at -the higher temperatures to result in a satisfactory bond.

In the form of the invention shown in Fig. l, the switch envelope III is made of glass and contains a quantity of mercury l I. A pair of electrodes l2 and B are sealed through the bottom of the envelope, the latter electrode being enclosed within a glass sleeve II for a portion of its height. The sleeve I 4 has a bulge l5 which acts as a seat for a spring IS, the upper end-of which is spread out, as indicated at H, to yieldingly restrainthe displacer, generally designated ll, from striking the bottom of the switch envelope.

The displacer It comprises an inner sleeve 19 of glass, ceramic or other light weight, non- .washer being held in place by coil spring in a mercury switch.

, 21,061 two factors which contribute to the formation magnetic material, and an outer sleeve 20 of magnetic material. The inner sleeve I8 has its lower end enlarged to form a shoulder 2| on which the outer sleeve 20 is mounted. Guide washers are carried by the displacer for guiding its movement within the switch envelope, the top A ceramic cup 21 is mounted on the projecting end of the electrode l3 and contains a pool of mercury 28 which is in contact with the end of w the electrode I3.

In practice, the cup is secured in place before the electrodes I2 and I3 are pinchseaied into the envelope. After the glass sleeve I I has been heat bonded to the electrode, preferably made of molybdenum, and the spring I6 has been telescoped over the sleeve l4 so as to rest upon the bead I5 formed on the sleeve, the ceramic cup 21, which is drilled to receive the end of the electrode I3, is slipped into place and heat is supplied to the juncture between the'two materials. Sufficient heat is applied to cause the glass to flow into the interstices of the ceramic material and the result is a bond which is exceptionally strong. I 3 ,A coil 29 is associated with the switch and when it is energized the dispiacer I8 is drawn downwardly, causing the. mercury level to rise above the lower edge of the cup 21 and make contact with the mercury pool 28, .thus closing the circuit between the electrodes l2. and I! through the body of mercury ll. When the coil is deenergized, the-displacer rises and the-mercury level i'alls, thus breaking the circuit.

The ceramic material of which the cup 21 is formed is sufliciently refractory to withstand the deteriorating effects of the electric are formed on high inductive loads, and preferably the inner sleeve IQ of the displacer I8 also has good refractory properties. The ceramic material has infinitely superior refractory properties to the glass sleeve to which the ceramic material is fused. When the ceramic material is Alundum, it is furthermore characterized by its hardness, by having good dielectric properties, by having the fusing temperature substantially above 1600 F., by being nonpowdering', and by having an unglazed orroughened surface. This latter property of the ceramic material is extremely important where the ceramic is being used as a part of. the

It should be noted that in Fig. 1 the fused bond between the ceramic cup 21 and the glass sleeve I4 is below the lowest level to which the mercury fill falls during the operation of the switch. This means that the joint is kept relatively cool by the surrounding body ofmercury, and it also emphasizes the importance of having a bond which is entirely impervious to mercury. When cements are used at this joint in place of a fused bond, a slight breaking down of the cement will greatly reduce the ability of the switch to stand up under a high voltage across the electrodes when the switch is in open position. In other words, the fused joint greatly increases the dielectric con stant for the switch.

Certain types of ceramic material give oil a powder which is readily discernible when used This powder contaminates the mercury and. interferes with its free movement to and from contact closing position. It i also increases the contact resistance of the switch. It is for this reason that a ceramic material that is non-powdering is preferred for use in accordance with the teachings of this inven tion.

In Fig. 2 another type of mercury switch is shown, this one being ordinarily called a combination front and back contact switch. In this switch three electrodes 30, II and 32 are sealed through the base of a switch envelope 34, which contains a quantity of mercury 35, the electrode 3|) always being in contact with the mercury, and the electrodes 3| and 32, each of which is insulated from the mercury fill by a glass sleeve 35 for a portion of its height, being adapted to be intermittently but never simultaneously in contact with the mercury.

A displacer, generally designated 3], which comprises a glass thimble 38, to the upper part. of which an iron sleeve 39 is secured by a spring 40 tightly telescoped over the top of the thimble, moves in response to a coil 4| to determine the condition of the electrical circuit between the electrodes. When the coil is energized the displacer moves upwardly in its effort to close the air gap 42 between pole pieces 43 and 44, and in so doing the mercury level recedes sufliciently to uncover the bare end 45 of the electrode 32 and at the same time the displacer, by being lifted above the bare end 46 of the electrode 3|, permits mercury to come into contact with the latter electrode.

Upon deenergizing the coil 4| the reverse operation takes place; that is, the thimble 38 caps the central electrode 3| and forces mercury away from the bare end 46 of that electrode, and at th same time displaces sufficient mercury to cover the bare end 45 of the electrode 32. The parts of the switch are so proportioned that at no time is it possible for the mercury to make contact simultaneously with both the electrodes 3| and 32.

When the switch is to be used service, it is necessary to provide some protection for the parts of the switch made of glass, for otherwise the are formed during the making and, breaking of the circuit will have a pronounced tendency to disintegrate or devitrify the glass. i

Accordingly, formed pieces of ceramic material are fused to the glass at strategic places; i. e., a ceramic collar 41 is fused within the lower portion of the thimble 38 at the place where the making and breaking of the circuit through the electrode 3| takes place. Likewise, the glass sleeves 36 of the electrodes 3| and 32. are topped with short sections of ceramic material, such as indicated at 4B, 'and these sections are fused to the sleeves 38 in the same manner that the cup 21 of.-the switch in Fig. 1 is fused to the sleeve In order to keep the over-all dimensions of the switch to a minimum, the electrode 32 is positioned within an elongated protuberance 49 in the lower side wall of the switch envelope and the portion of the protuberance which is immediately adjacent to the bare end 45 of the electrode 32 may be protected from the electric are by fusing a formed piece of ceramic 50 to the envelope, as shown in Fig. 2.

In Fig. 3 a switch is shown which is somewhat similar to that shown in'Fig. 2, except that the switch has only two electrodes and a time delay element is incorporatedin the switch for delayin; the movement of mercury to and/or away for heavy duty from the central electrode. The principle upon material, the plug being fused into an opening provided in the top of the glass thimble 52. This method of attaching the ceramic time delay element to the displacer is much superior to that disclosed in Larson Patent #l,96'7,94'1, issued'July 24, 1934, not only because it increases the life of the switch due to the elimination of cementitious substances, but also because it is easier to manufacture a switch in which the ceramic material is fused into place.

Preferably the switch is also provided with a collar 53 and sleeve 54 of ceramic material, both parts being similar in all respects with the collar 41 and sleeve 48 shown in the switch of Fig. 2.

Th switch shown in Fig. 4 is of the type disclosed in Larson Patent #1367346, issued July 24, 1934, but instead of securing the ceramic thimble 55 to the central electrode 56 by cement, as disclosed in Larson Patent #l,96'7,946, a small section 51 of glass is fused to the end of the electrode 56, and to this section of glass the cup 55 is fused.

The above specific disclosures are but a few of the ways in which ceramic material may be terials. is absolutely impervious so .there is no chance for mercury to make contact with the electrode material. v}

In practice, the fusion of the glass with the ceramic material is accomplished by heating the two parts-to, be fused together to a temperaturev which will cause the glass to flow and bond itself with the ceramic material, and the joint is then slowly cooled to room temperature.

Throughout the specification and claims all values for coeflicients of expansion refer to those which obtain for room temperatures; also, the word parallel as it is used in describing the relationship between two expansion curves is not to be construed in its strict sense, but rather in the sense that the curves at no temperature within the range of interest move apart more than some given amount, or, in other words, the curves are closely parallel. Obviously the curves may even cross one another and still be parallel in the sense in which the term parallel is used herein.

Although certain specific examples have been cited in the specification for glass and ceramic materials that will satisfactorily fuse together, it will be understood that the invention is not limited to these speciflcmaterials and that other materials which have parallel expansion curves, in the sense in which that term is here employed, and which have the characteristics and qualities called for in the claims, are included within the scope of this invention.

I claim as my invention:

that are superior it is fused.

of mercury fill, said 2. In amercury switch, the combination of a switch envelope, a mercury flll, spaced electrodes in theenvelope one of which is adapted to be intermittently placed in electrical contact with the main body of the mercury fill, a glass sleeve surrounding at least a portion of said one electrode, and a ceramic sleeve fused to the glass sleeve, the glass being a low expansion borosilicate, and the ceramic being a preformed body characterized by having refractory properties that are superior to those of the glass to which it is fused, said ceramic and glass sleeves having linear expansion curves which are substantially coincident with or closely parallel to one another over a wide range of temperature change.

3. The combination of a switch envelope, a mercury fill, spaced electrodes in the envelope, one of which is adapted to be intermittently Placed in electrical contact with the main body of mercury fill, said' electrodes being positioned relatively close to a part of the switch which has relatively poor refractory properties so that it is subject to the deteriorating efiects of the are formed at said electrode, and means protecting said part of the switch from the arc comprising a preformed refractory ceramic member fused to a contiguous glass member, said glass being a low expansion borosilicate, and the ceramic having refractory properties that are superior tothose of theglass to which it is fused.

4. In a mercury switch, the combination of a switch envelope, amercury'fill, spaced electrodes in the envelope one of which is adapted to be intermittently placed in electrical contact with the main body of the mercury fill, a glass member' associated with said one electrode, and a ceramic member fused to the glass member, the

glass being a low expansion borosilicate, and the ceramic being a lzed by having refractoryproperties that are superior to those of the glass to which it is fused, said ceramic and glass members having linear expansion curves which are substantially coincident with or closely parallel to one another over a wide range of temperature change, and said ceramic member serving as a cup "for supporting a body of mercury in constant'contact with said oneelectrodeu o. 7, '5. 'I'he combination of a switch envelope, a

mercury fill, spaced electrodes in the envelope,

one ofwhich is adapted to be intermittently placed in electrical contact withthe main body relatively cloae to a glass part of the switch poor refractorylpl'operties so that it"ls subieet' to the deteriorating effects of them "formed at" said'elec'trode, and means protecting saidpart of arc comprising a preformed refractory 'ce'ramic'memberfuisedtosaidglassparhtheglass'beinga preformed body characterelectrodes being positioned 6. In a mercury switch, the combination of a switch envelope, a mercury fill, a gas fill, spaced electrodes in the envelope one of which is adapted to be intermittently placed in electrical contact with the main body of the mercury fill, a thimble telescoped over said one electrode and provided with a gas pervious wall for permitting gas to pass at a controlled rate between the inside and outside of the thimble, a. part of the thimble being of glass and a part being of ceramic material, the glass being a low expansion borosilicate and the ceramic being fused to the glass and being a preformed body characterized by having refractory properties that are superior to the glass.

7. In a mercury switch, the combination of a switch envelope, a mercury fill, spaced electrodes in the envelope one of which is adapted to be intermittently placed in electrical contact with the main body of the mercury fill, a glass sleeve surrounding at least a portion of said one electrode and heat bonded to it, and a ceramic sleeve fused to the glass sleeve, the glass being a low expansion borosilicate, and the ceramic being a pre-formed body characterized by having refractory properties that are superior to those of the glass to which it is fused, the ceramic and glass sleeves having linear expansion curves which are substantially coincident with or closelyparallel to one another and to. the corresponding curve for the material of which said one electrode is formed, over a wide range of temperature change.

"8. In a mercury switch, the combination of a switch envelope, a mercury fill, spaced electrodes in the envelope one of which is adapted to be intermittently placed in electrical contact with the main body of the mercury fill, surrounding at least a portion of said one electrode and heat bonded to it, and a ceramic sleeve fused to the glass sleeve, the glass being a low expansion borosilicate and the ceramic being a pre-formed body characterized by having refractory properties that are superior to those of the glass to which it is fused, the ceramic and glass sleeves having linear expansion curves which are substantially coincident with or closely parallel- 'the main body of the mercury fill, a glass sleeve surroundingat least a'portion of said one electrode, and a ceramicsleeve fused to the glass sleeve. the glass being a low expansion borosilicate having approximately the following percentage composition:

s10: v V 7 7e A120: 4.5 N820 V e 5 K:O.- I 2.5 H00: nu 11 and the ceramic being a ore-formed body characterized by having refractoryproperties that are superior tothose of the glassto whichitisfused and by being composed mainly of aluminum oxide.

a glass sleeve 10. In a circuit breaker of the mercury contact typ the combination of a switch envelope, a mercury fill, spaced electrodes in the envelope, one of which is made of molybdenum and projects upwardly through the mercury fill, said one electrode being covered for a portion of its length with an insulating sleeve leaving an exposed end adapted to be intermittently placed in contact with the main body of mercury as it rises and falls with respect-to the exposed end, said insulating sleeve being formed in two parts, the lower one of which is made of a borosilicate glass having a coefficient of expansion that enables it to be heat bonded to the electrode which it encloses, and. the upper part being made of a hard preformed ceramic material having refractory properties that are superior to those of the glass supporting the ceramic and having an expansion curve that-is substantially parallel to the expansion curve of the glass.

11. In a mercury switch, the combination of a switch envelope, a mercury fill, spaced electrodes cury whereby the glass is protected from the heat of the are by the surrounding body of mercury, the glass having properties permitting it to be fused directly with the ceramic.

14. In a circuit breaker of the mercury contact type, the combination of a switch envelope, a mercury fill, spaced electrodes in the envelope, means for shifting the mercury fill from a low level to a high level to change the condition of the electrical circuit through the electrodes, one of said electrodes projecting upwardly through the mercury fill and being surrounded for at least a portion of its length with an insulating sleeve leaving an exposed end adapted to be intermittently placed in contact with the main body of mercury as the mercury fill rises and falls along the insulating sleeve in response to the mercury shifting means, said insulating sleeve comprising a lower glass portion to which an upper ceramic portion is fused, the ceramic being a pre-formed body serving as a cup for supporting a body of mercury in constant contact in the envelope one of is adapted to be said one electrode and having relatively intermittently placed in electrical contact with the main body of the mercury fill, a glass member associated with said one electrode, a ceramic member fused to the glass member, the glass being a low expansion borosilicate and the ceramic being a pre-formed body characterized by having refractory properties that are superior to those of the glass to which it is fused and by having an unglazed outer surface, said ceramic and glass members having linear expansion curves which'are substantially coincident with or closely parallel to one another over a wide range of temperature change, and said ceramic memone of which projects upwardly through the mercury fill and is covered for a portion of its length with an insulating-sleeve leaving an exposed end adapted to be intermittently placed in contact with the main body of mercury as the mercury fill rises and fallsxalong the insulating sleeve.

said insulating sleeve comprising a lower glass portion to which an upper ceramic portion is fused, the glass being a low expansion'borosilicate and the ceramic being a pre-formed body characterized by its hardness, roughened surface, and refractory properties which are superior to those of the glass.

13. In a circuit breaker of the mercury contact type, the combination of a switch envelope, a mercury fill, spaced electrodes in the envelope, means for shifting the mercury fill from a lowlevel to a high level to change the condition of the electrical circuit through the electrodes, one of said electrodes projecting upwardly through the mercury fill and being surrounded for at least a portion of its length with an insulating sleeve leaving an exposed end adapted to be intermittently placed in contact with the main body of mercury as the mercury fill rises and falls along the insulating sleeve in response to the mercury shifting means, said insulating sleeve comprising a lower glass portion to'which an upper ceramic portion is fused, the ceramic being a pre-formed body characterized by having refractory properties that are superior to the glass to which it is fused and the fused joint between the glass and the ceramic being below the low level of the merstraight vertical side walls formed of a ceramic material that is characterized by having refractory properties superior to those of the glass to which it is. fused, by having an unglazed outer surface, and the fused joint between the glass and the ceramic being below the low level of mercury whereby the glass is protected from the heat of the arc by the surrounding body of mercury.

15. In a mercury switch, the combination of a switch envelope, a mercury fill, spaced electrodes in the envelope, one of which is adapted to be intermittently placed in electrical contact with the main body of the mercury fill, a glass sleeve surrounding at least a, portion of said one electrode, and a ceramic sleeve fused to the glass tact type, the combination of a switch envelope,

a mercury fill, spaced electrodes in the envelope one of which projects upwardly through the mercury fill, said one electrode being covered for a portion of its length with an insulating sleeve leaving an exposed end adapted to be intermittently placed in contact with the main body of mercury as it rises and falls with respect to the exposed end, said insulating sleeve being formed in two parts, the lower one of which is made of a borosilicate glass having a coefficient of expansion that enables it to be heat bonded to the electrode which it encloses and the upper part being made of a hard pre-formed ceramic materlal having refractory properties which are superior to those of the glass to which it is fused and having an expansion curve which, over a wide range of temperatures, is relatively close to the corresponding curve for the glass. 17. In a circuit breaker of themercury contact type, the combination of a switch envelope, a mercury fill,'spaced electrodes in the envelope one of which is molybdenum and projects upwardly through the mercury fill, said one electrode being. covered for a portion of its length with an insulating sleeve leaving an exposed end adapted to be intermittently placed in contact with the main bodyof mercury as it rises and falls with respect to the exposed end, said insuone of which is made of a borosilicate glass having a coeflicient of expansion that enables it to be heat bonded to he electrode which it encloses and the upper p being made of a hard preformed ceramic material having refractory properties which are superior to those of the glass to which it is fused and having an expansion curve which over a wide range of temperatures, is relatively close to the corresponding curve for the glass, the coeflicient of linear expansion for the ceramioand glass at room temperature each being not more than 5.4 x 10-;

18. In a circuit breaker of the mercury contact type, the combination of a switch envelope, a mercury fill, spaced electrodes in the envelope, means for shitting the mercury 1111 from a low level to a high level to change the condition of the electrical circuit through the electrodes, one

the mercury fill and being covered fora portion of its length with an insulating sleeve leaving an exposed end adapted to be intermittently placed in contact with the main body of mercury as the mercury fill rises and Ialls along the insulating sleeve in response to the mercury shifting means, said insulating sleeve comprising a lower glass portion to which an upper ceramic portion is fused, the ceramic being -a pr'e-formed body characterized by being substantially non-powdering and by having refractory properties that are superior to the glass to which it is fused,

and the fused joint between the glass and the whereby the glass is protected from the heat of the arc by the surrounding body of mercury.

CARL H. LARSON. 

